Webworms are common garden pests known for their distinctive silken webs that envelop tree branches and foliage. They become noticeable in landscapes, particularly during late summer and early fall. Their activity focuses on feeding within these protective webs. While webworms can cause visible damage, understanding their life cycle and habits helps manage populations effectively.
Recognizing Webworms
Webworms, specifically fall webworms (Hyphantria cunea), are identified by the communal, tent-like webs they construct on tree branches. These webs can range from small, softball-sized enclosures to much larger structures, sometimes covering entire limbs, and are typically spun around leaves. The webs serve as protective shelters for developing larvae.
Inside these silk enclosures, the larvae, which are caterpillars, can be observed. These caterpillars are usually pale yellow or green, with black spots and tufts of long, wispy hairs. They measure approximately one inch when mature. The adult form of the webworm is a white moth, often with small black spots on its wings, which lays eggs on the underside of leaves. Webworms infest a variety of deciduous trees, including pecan, mulberry, sweetgum, and fruit trees, as well as some shrubs.
Understanding Webworm Impact
Webworm larvae damage leaves by feeding within their silken webs. As caterpillars grow, they expand their webs to encompass more foliage, continuously consuming the leafy tissue inside. This feeding activity leads to defoliation, where leaves within the web are skeletonized, leaving only veins.
Affected branches will show brown, shriveled leaves encased in silk. While the aesthetic impact can be significant, particularly on ornamental trees, mature trees generally tolerate this defoliation without lasting harm. Young or newly planted trees, however, may experience increased stress and stunted growth due to lost photosynthetic leaf area. Repeated severe infestations over several years can weaken a tree, making it more susceptible to other stressors.
Effective Webworm Control
Managing webworm infestations often begins with physical removal, especially for accessible webs. Smaller webs can be pruned from branches using long-handled pruners or by hand. Remove the entire web, including caterpillars, and dispose of it away from desirable plants.
For out-of-reach webs, a strong stream of water from a garden hose can dislodge them, exposing caterpillars to predators and the elements. This method is most effective when webs are small and caterpillars are young. Another effective biological control involves applying products containing Bacillus thuringiensis (Bt). This naturally occurring bacterium, when ingested by caterpillars, disrupts their digestive system, leading to their demise. Bt is a selective insecticide, targeting caterpillars and harmless to other organisms, including beneficial insects. Chemical insecticides are a last resort and are not necessary, as webworms rarely cause permanent damage to established trees.
Recognizing Webworms
Webworms, specifically fall webworms (Hyphantria cunea), are identified by the communal, tent-like webs they construct on tree branches. These webs can range from small, softball-sized enclosures to much larger structures, sometimes covering entire limbs, and are typically spun around leaves. The webs serve as protective shelters for developing larvae.
Inside these silk enclosures, the larvae, which are caterpillars, can be observed. These caterpillars are usually pale yellow or green, with black spots and tufts of long, wispy hairs. They measure approximately one inch when mature. The adult form of the webworm is a white moth, often with small black spots on its wings, which lays eggs on the underside of leaves. Webworms infest a variety of deciduous trees, including pecan, mulberry, sweetgum, and fruit trees, as well as some shrubs.
Understanding Webworm Impact
Webworm larvae damage leaves by feeding within their silken webs. As caterpillars grow, they expand their webs to encompass more foliage, continuously consuming the leafy tissue inside. This feeding activity leads to defoliation, where leaves within the web are skeletonized, leaving only veins.
Affected branches will show brown, shriveled leaves encased in silk. While the aesthetic impact can be significant, particularly on ornamental trees, mature trees generally tolerate this defoliation without lasting harm. Young or newly planted trees, however, may experience increased stress and stunted growth due to lost photosynthetic leaf area. Repeated severe infestations over several years can weaken a tree, making it more susceptible to other stressors.
Effective Webworm Control
Managing webworm infestations often begins with physical removal, especially for accessible webs. Smaller webs can be pruned from branches using long-handled pruners or by hand. Remove the entire web, including caterpillars, and dispose of it away from desirable plants.
For out-of-reach webs, a strong stream of water from a garden hose can dislodge them, exposing caterpillars to predators and the elements. This method is most effective when webs are small and caterpillars are young. Another effective biological control involves applying products containing Bacillus thuringiensis (Bt). This naturally occurring bacterium, when ingested by caterpillars, disrupts their digestive system, leading to their demise. Bt is a selective insecticide, targeting caterpillars and harmless to other organisms, including beneficial insects. Chemical insecticides are a last resort and are not necessary, as webworms rarely cause permanent damage to established trees.